Which of the following pigments does NOT absorb yellow/orange light (650-750nm)?

• A. Chlorophyll a.
• B. Carotenoids.
• C. Chlorophyll b.
• D. Both a and c.

Answer: (B)

Verified step by step guidance

1. Identify the wavelength range given in the problem: yellow/orange light corresponds to wavelengths from 650 nm to 750 nm, which actually falls within the red to near-infrared region of the light spectrum.
2. Recall the absorption spectra of the pigments involved: Chlorophyll a primarily absorbs light in the blue (~430 nm) and red (~660 nm) regions, Chlorophyll b absorbs mostly in the blue (~450 nm) and some in the red-orange (~640 nm) regions, while Carotenoids absorb mainly in the blue to green range (~400-550 nm) and do not absorb significantly in the 650-750 nm range.
3. Represent the absorption ranges using LaTeX notation for clarity: Chlorophyll a absorbs at approximately \(430\,\text{nm}\) and \(660\,\text{nm}\), Chlorophyll b absorbs at about \(450\,\text{nm}\) and \(640\,\text{nm}\), and Carotenoids absorb roughly between \(400\,\text{nm}\) and \(550\,\text{nm}\). Since the problem's range is \(650-750\,\text{nm}\), compare these values to determine which pigment does not absorb in this range.
4. Analyze the overlap between the pigments' absorption ranges and the given wavelength range \(650-750\,\text{nm}\). Chlorophyll a has absorption near \(660\,\text{nm}\), which falls within this range, Chlorophyll b's absorption near \(640\,\text{nm}\) is just below this range but close, and Carotenoids do not absorb in this range at all.
5. Conclude which pigment does not absorb yellow/orange light (650-750 nm) based on the comparison of absorption spectra without explicitly stating the final answer.